Method and system for delta double sampling
First Claim
1. A method for detecting a chemical reaction, the method comprising:
- inducing a chemical reaction within a well coupled to a chemically-sensitive transistor, the chemically-sensitive transistor selectively coupled to a circuit node via a select transistor;
operating the select transistor in a first mode during a first time interval of the chemical reaction, and sampling a reference signal at the circuit node;
operating the select transistor in a second mode during a second time interval of the chemical reaction, and sampling a sensor signal at the circuit node; and
normalizing the sampled sensor signal using the sampled reference signal to produce an output signal.
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Abstract
An array of sensors arranged in matched pairs of transistors with an output formed on a first transistor and a sensor formed on the second transistor of the matched pair. The matched pairs are arranged such that the second transistor in the matched pair is read through the output of the first transistor in the matched pair. The first transistor in the matched pair is forced into the saturation (active) region to prevent interference from the second transistor on the output of the first transistor. A sample is taken of the output. The first transistor is then placed into the linear region allowing the sensor formed on the second transistor to be read through the output of the first transistor. A sample is taken from the output of the sensor reading of the second transistor. A difference is formed of the two samples.
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Citations
11 Claims
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1. A method for detecting a chemical reaction, the method comprising:
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inducing a chemical reaction within a well coupled to a chemically-sensitive transistor, the chemically-sensitive transistor selectively coupled to a circuit node via a select transistor; operating the select transistor in a first mode during a first time interval of the chemical reaction, and sampling a reference signal at the circuit node; operating the select transistor in a second mode during a second time interval of the chemical reaction, and sampling a sensor signal at the circuit node; and normalizing the sampled sensor signal using the sampled reference signal to produce an output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification